Microelectronic packages, called "multi chip modules" or "hybrids", are assembled using unpackaged semiconductor dice. Prior to the assembly procedure, each unpackaged die must be tested to measure its quality and reliability. This has led to the development of test procedures suitable for testing unpackaged semiconductor dice. Known-good-die (KGD) refers to an unpackaged die having the same quality and reliability as the equivalent packaged die.
Testing includes burn-in testing wherein the dice are heated while the integrated circuits are electrically biased. In addition, the dice are subject to speed and functionality tests to check the performance of the integrated circuits and devices formed on the dice. Among the parameters tested are input and output voltages, capacitance and current specifications. Memory chips are also put through logic tests wherein data storage, retrieval capabilities and response times are measured.
For testing and burning-in unpackaged dice, temporary carriers have been used in the manufacturing process in place of conventional single chip packages. This type of carrier typically includes a base for retaining and housing a single die. The carrier also includes an interconnect that allows a temporary electrical connection to be made between an individual die and external test circuitry. Carriers for testing unpackaged dice are disclosed in U.S. Pat. No. 4,899,107 to Corbett et al., U.S. Pat. No. 5,302,891 to Wood et al. and U.S. Pat. No. 5,408,190 to Wood et al., which are commonly assigned with the present application.
One of the key design considerations for a carrier is the method for establishing a temporary electrical connection with the bond pads on the die. With some carriers, the die is placed circuitry side down in the carrier and biased into contact with the interconnect. The interconnect contains the contact structure that physically aligns with and contacts the bond pads of the die. Exemplary contact structures include wires, needles, and bumps. The mechanisms for making electrical contact include piercing the native oxide of the bond pad with a sharp point, breaking or burnishing the native oxide with a bump, or moving across the bond pad with a contact adapted to scrub away the oxide. In general, each of these contact structures is adapted to form a low-resistance contact with the bondpad.
With this method for testing unpackaged semiconductor dice, it is preferable to perform the test procedure without damaging the die. The bond pads of a die are particularly susceptible to damage by the contact structure of the carrier during formation of the temporary electrical connection. It is also advantageous for the contact structure on the carrier to compensate for differences in the vertical location of the bond pads.
Besides testing of unpackaged dice to form known good die, it is sometimes necessary to establish a temporary electrical connection with semiconductor dice contained on a semiconductor wafer. As an example this can occur in the testing of the dice before singulation from the wafer. It is also sometimes necessary to establish a permanent electrical connection between unpackaged dice such as in the formation of multi chip modules.
The present invention is directed to an improved compliant interconnect suitable for establishing a temporary or permanent electrical connection with bond pads or other contact locations on a semiconductor die. The interconnect is adapted to make a low resistance electrical connection with a die without damaging the bond pads of the die. In addition the interconnect can be formed of a material such as silicon having a thermal coefficient of expansion matching that of a semiconductor die or wafer.
In view of the foregoing it is an object of the present invention to provide an improved compliant interconnect for semiconductor dice and a method for forming the interconnect.
It is yet another object of the present invention to provide an improved method for making a temporary or permanent electrical connection to semiconductor dice.
Other objects, advantages, and capabilities of the present invention will become more apparent as the description proceeds.